In general, a display apparatus refers collectively to TV's or computer monitors, etc. and includes a display device for displaying images and a housing for holding the display device.
Display devices include, for example, a plasma display panel (PDP), a liquid crystal display (LCD), an electrophoretic display, a cathode-ray tube (CRT), and an organic light emitting diode (OLED) display. A display device has RGB pixel patterns and optical filters.
The optical filter may comprise at least one of the following elements: an anti-reflection film for preventing external incident light from being reflected toward the outside; a near-infrared ray blocking film for blocking the emission of near-infrared rays generated in the display device in order to prevent erroneous operation of a device such as a remote controller; a color compensation film including a color control dye which controls the color tone to enhance color purity; and an electromagnetic wave shielding film for shielding electromagnetic waves generated in the display device during the operation of the device. Here, the electromagnetic wave shielding film includes a transparent base material and metal mesh patterns on the base material.
Meanwhile, with the rapid popularization of electronic devices such as smart phones, tablet PCs, and internet protocol televisions (IPTVs), there is an increasing need for a touch function to input information by hand without using a special input device such as a keyboard or a remote controller. In addition, there is a need for a multi-touch function to recognize specific points and to write information.
Touch panels having the above-mentioned functions can be divided according to a signal detection method into the following types: a resistive-type touch panel which senses a pressed position based on a change in an electric current or voltage value in a state in which DC voltage is applied; a capacitive-type touch panel which utilizes a capacitance coupling in a state in which AC voltage is applied; and an electromagnetic-type touch panel which senses a selected position based on a change in voltage in a state in which a magnetic field is applied.
Among these touch panels, the most popularized resistive-type and capacitive-type touch panels employ a transparent conductive film such as an ITO film to recognize a touch by electrical contact or based on a change in capacitance. However, the transparent conductive film generally has a high resistance of 150 ohms per square or more, and thus the sensitivity of the touch panel comprising the conductive film decreases as the size thereof becomes larger. In addition, an increase in the size of the touch screen leads to a rapid increase in the cost of the ITO film. These problems make it difficult to commercialize these touch panels. In an attempt to overcome these problems, the use of highly conductive metal patterns to realize large-sized touch panels has been proposed.